Agriculture Reference
In-Depth Information
of N, via its ef ects on the root system, leading to a general yellowing of the
entire plant. Zinc defi ciency is usually found in eroded areas, in soils with
high amounts of coral sand and in soils with high pH. Defi ciency causes the
younger leaves to curve and twist; the symptom is unique and diagnostic.
When Zn defi ciency is severe, apical dominance is lost and plants sucker
profusely. Zinc sulfate 0.5% (w/v), applied at 935 l/ha, is sprayed as needed.
Boron defi ciency is characterized by chlorosis of young leaves, development
of red margins and even death of the apical region, resulting in profuse
suckering. Boron defi ciency is a common problem in Australia and 1-4 ppm
boron is applied with ethephon at the time of forcing.
The nutrient requirements of pineapple in Hawaii are based on the
concept of the crop log, which involves the development of laboratory soil and
foliar indices, visual defi ciency symptoms for N, Fe and Zn, and others that
measure growth rate, pathogens, root parasites, moisture stress and weather
conditions (Sanford, 1964; Malezieux and Bartholomew, 2003). A crop log
not only indicates defi ciency symptoms but also attempts to determine causes
of defi ciencies. Soil and foliar analyses are both important, as the former
shows reserve amounts of soil nutrients and the latter indicates ei ciency in
absorption. An element may be sui cient in the soil but defi cient in the plant,
due to causes such as moisture stress, root disease or loss of the root system to
pests, or an elemental imbalance causing unfavourable interactions af ecting
absorption (Sanford, 1962). Fertilizer is applied on a schedule to meet dif erent
requirements at dif erent stages of growth (Table 12.3). Foliar applications
should cease after forcing to prevent injury to the infl orescence and reduced
fruit yields.
Chemical fl ower induction
The accidental discovery in the Azores that smoke from burning organic
materials induces premature fl owering in greenhouse-cultured pineapples
led to the wide practice of burning rubbish around the periphery of the
fi elds in Puerto Rico (Rodriguez, 1932). The active ingredient in the smoke
is ethylene gas, with acetylene and calcium carbide also inducing fl owering
in pineapple (Aldrich and Nakasone, 1975). Forcing plants into fl owering
allows synchronization of harvest and makes it possible to control harvest
dates to meet anticipated fresh market and cannery needs (Fig. 12.7). Fruit
harvest date can be predicted with good accuracy with only daily maximum
and minimum air temperature to calculate fruit heat units (Malezieux et al. ,
1994). This model can be adjusted using historical data.
The relatively soluble sodium salt of alpha-naphthaleneacetic acid (SNA)
was the fi rst plant growth regulator used commercially to force fl owering
in Hawaii (Bartholomew and Criley, 1983). Ethylene and acetylene gases
dissolved in water have been used in many pineapple-growing regions. The
 
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